Power Systems calculator
Power Factor Correction Calculator
Enter balanced three-phase real power, current power factor, target power factor, and line-to-line voltage to screen the capacitor kVAR needed for correction. The calculator uses Qc = P × (tan phi1 - tan phi2), then compares before/after kVA and balanced line current so the result stays tied to your motor, feeder, transformer, or plant-load data.
Updated July 10, 2026
Enter balanced three-phase kW, current PF, target PF, and line voltage to compare capacitor kVAR, before/after kVA, and line-current reduction.
Qc = P × (tan φ1 - tan φ2) | Before kVA = kW ÷ PF | Line current = kVA ÷ (√3 × kV)
Enter balanced three-phase kW, current PF, target PF, and line voltage to screen capacitor kvar, kVA, and line-current reduction
Example Calculations
How to Use
How to use the power factor correction calculator
- Enter the balanced three-phase real power in kW.
- Enter the measured current power factor and the desired target power factor.
- Select the actual line-to-line voltage of the system, or use the custom-voltage option when the service does not match a common preset.
- Review the required capacitor rating, the change in kVAR, the before/after kVA, and the before/after line current.
- Treat the output as a screening answer only, then confirm tariff rules, harmonic conditions, switching steps, and the actual capacitor-bank design before installation.
Use the calculator for the actual installation data before comparing catalog capacitor steps. The reference sections below explain what each output means, but they are not a substitute for entering the measured load and voltage.
What the page returns
| Output | Meaning | How to use it |
|---|---|---|
| Required capacitor rating | Reactive power the capacitor bank must supply to move from the current PF to the target PF | Start a catalog review for standard capacitor-bank steps |
| Current and target kVA | Apparent power before and after correction | Estimate how much source kVA demand and upstream loading could drop |
| Current and target line current | Balanced three-phase line current before and after correction | Screen feeder, breaker, and transformer loading changes |
| Line-current reduction | Absolute and percentage current reduction from the selected correction target | Use it as an early indicator of whether correction will materially free capacity |
Important scope notes
- This page assumes a balanced three-phase load. Single-phase and heavily unbalanced systems need a different review.
- The page does not claim direct kWh savings, tariff savings, or payback. Those depend on the real tariff basis, load profile, and loss analysis.
- It does not size detuned banks, harmonic filters, switching steps, or leading-PF protection logic.
- Targets above about 0.98 can become risky under light load, especially if the correction is fixed rather than staged.
Calculator workflow example
Try the common plant-load preset, then change the kW, measured PF, target PF, and voltage to match the job. The result area will calculate capacitor kVAR, before/after apparent power, and line-current change from those inputs.
Use the Power Factor Calculator for the base power triangle, the Power Factor Penalty Calculator when the real question is a utility billing threshold, the Motor Current Calculator for motor-load current screening, and the Transformer Calculator when you need the upstream transformer current and kVA view.
Common Applications
More applications. Open to review 2 additional use cases.
Frequently Asked Questions
How does the calculator find required capacitor kvar?
It uses Qc = P × (tan φ₁ − tan φ₂), where P is real power in kW, φ₁ is the angle from the current power factor, and φ₂ is the angle from the target power factor. That gives the reactive power the capacitor bank must supply on a balanced three-phase basis.
Why does the page show kVA and line current as well as capacitor kvar?
Because many users need more than the capacitor size. The practical reason to improve power factor is usually lower source kVA demand or lower line current, so the page shows those before/after values directly.
Why does this page not estimate energy savings or payback?
Because power factor correction does not automatically translate into a reliable kWh-savings number on every tariff or load profile. The financial answer depends on the actual billing basis, demand terms, operating profile, and real loss analysis.
Can I use this page for a fixed capacitor bank on a lightly loaded system?
Use caution. A fixed bank can push a lightly loaded system toward leading power factor, which is why very high targets and variable loads usually deserve staged or automatically switched correction instead of one fixed step.
When do I need a harmonic or detuning review?
Whenever the system has significant nonlinear loads such as VFDs, rectifiers, or other electronic power converters. In those cases, a simple kvar answer is not enough because resonance and switching behaviour matter.
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